Lubricating oil composition

ABSTRACT

A lubricating oil composition having a sulfur content of up to about 0.4 wt. % and a sulfated ash content of up to about 0.5 wt. % as determined by ASTM D874 is disclosed which comprises (a) a major amount of an oil of lubricating viscosity; (b) at least one oil-soluble or dispersed oil-stable boron-containing compound having no more than about 400 ppm of boron; and (c) at least one oil-soluble or dispersed oil-stable molybdenum-containing compound having, at least about 1100 ppm of molybdenum, based upon the total mass of the composition; wherein the lubricating oil composition has a ratio of sulfur to molybdenum of less than or equal to about 4:1.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention generally relates to lubricating oil compositions.

2. Description of the Related Art

Exhaust after-treatment devices, equipped on internal combustion enginesto comply with emission regulations, have proven to be sensitive to thecombustion by products of the fuel and lubricant used in the engine. Inaddition, certain types of devices are sensitive to one or more of thefollowing: (1) phosphorus coming from the lubricant, (2) sulfur comingfrom both fuel and lubricant, and (3) sulfated ash resulting from thecombustion of fuel and lubricant. In order to ensure the durability ofthe different types of after-treatment devices, special lubricants arebeing developed that feature relatively low levels of, for example,sulfur, phosphorus, and sulfated ash.

U.S. Patent Application Publication. No. 20050043191 (“the '191application”) discloses a lubricating oil composition having less than2000 ppm sulfur and free of zinc and phosphorus. The '191 applicationfurther discloses that the lubricating oil composition has a minimum of120 ppm of boron and a minimum of 80 ppm of molybdenum. Each of theexamples shown in Table 1 of the '191 application disclose an ashcontent of 0.96, 0.99 and 1.05 for Oils 1, 2, and 3, respectively.

U.S. Pat. No. 6,777,378 (“the '378 patent”) discloses a lubricating oilcomposition containing (a) a base oil; (b) a molybdenum- andsulfur-containing composition derived from a basic nitrogen-containingcompound, a molybdenum compound and carbon disulfide; (c) a borateester; and (d) optionally a phosphorus-containing compound provided thatthe phosphorus content of the composition does not exceed about 0.10 wt.%. The '378 patent further discloses that the lubricating oilcomposition has a boron content of about 30 ppm to about 600 ppm and amolybdenum content of about 25 ppm to about 800 ppm.

U.S. Pat. No. 7,026,273 (“the '273 patent”) discloses a lubricating oilcomposition containing a major amount of oil of lubricating viscosity,and a minor amount of a boron-containing additive, a detergent additivecomposition and one or more co-additives. The '273 patent furtherdiscloses that the lubricating oil composition has a boron content ofgreater than 150 ppm, a molybdenum content of at most 1000 ppm and lessthan 4000 ppm by mass of sulfur.

EP 0 737 735 (“the 735 application”) discloses a lubricant compositionproduced by blending (a) a Mo-containing friction conditioner; and (b) aB-containing compound with a lubricant base oil. The 735 applicationfurther discloses that the lubricating oil composition has a boroncontent of greater than 0.015 wt. % (150 ppm) and a molybdenum contentof 100 ppm to 2000 ppm.

It is desirable to develop improved lubricating oil compositions whichexhibit improved deposit reduction, as well as wear and oxidationinhibition when used in an internal combustion engine.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, alubricating oil composition having a sulfur content of up to about 0.4wt. % and a sulfated ash content of up to about 0.5 wt. % as determinedby ASTM D874 is provided which comprises (a) a major amount of an oil oflubricating viscosity; (b) at least one oil-soluble or dispersedoil-stable boron-containing compound having no more than about 400 ppmof boron, based upon the total mass of the composition; and (c) at leastone oil-soluble or dispersed oil-stable molybdenum-containing compoundhaving at least about 1100 ppm of molybdenum, based upon the total massof the composition; wherein the lubricating oil composition has a ratioof sulfur to molybdenum of less than or equal to about 4:1.

In accordance with a second embodiment of the present invention, thereis provided a method of operating an internal combustion engine whichcomprises operating the internal combustion engine with a lubricatingoil composition having a sulfur content of up to about 0.4 wt. % and asulfated ash content of up to about 0.5 wt % as determined by ASTM D874and comprising (a) a major amount of an oil of lubricating viscosity;(b) at least one oil-soluble or dispersed oil-stable boron-containingcompound having no more than about 400 ppm of boron, based upon thetotal mass of the composition; and (c) at least one oil-soluble ordispersed oil-stable molybdenum-containing compound having at leastabout 1100 ppm of molybdenum, based upon the total mass of thecomposition; wherein the lubricating oil composition has a ratio ofsulfur to molybdenum of less than or equal to about 4:1.

In accordance with a third embodiment of the present invention, there isprovided an internal combustion engine lubricated with a lubricating oilcomposition having a sulfur content of up to about 0.4 wt. % and asulfated ash content of up to about 0.5 wt. % as determined by ASTM D874and comprising (a) a major amount of an oil of lubricating viscosity;(b) at least one oil-soluble or dispersed oil-stable boron-containingcompound having no more than about 400 ppm of boron, based upon thetotal mass of the composition; and (c) at least one oil-soluble ordispersed oil-stable molybdenum-containing compound having at leastabout 1100 ppm of molybdenum, based upon the total mass of thecomposition; wherein the lubricating oil composition has a ratio ofsulfur to molybdenum of less than or equal to about 4:1.

The molybdenum-containing lubricating oil compositions of the presentinvention advantageously provide high wear inhibition when used in aninternal combustion engine while containing relatively low levels ofsulfated ash content. In addition, the high wear inhibition can beachieved with the molybdenum-containing lubricating oil compositions ofthe present invention while also employing relatively low levels (orsubstantially free) of any phosphorus and zinc content.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a lubricating oil compositionhaving a sulfur content of up to about 0.4 wt. % and a sulfated ashcontent of up to about 0.5 wt. % as determined by ASTM D874 andcontaining at least (a) a major amount of an oil of lubricatingviscosity; (b) at least one oil-soluble or dispersed oil-stableboron-containing compound having no more than about 400 ppm of boron,based upon the total mass of the composition; and (c) at least oneoil-soluble or dispersed oil-stable molybdenum-containing compoundhaving at least about 1100 ppm of molybdenum, based upon the total massof the composition; wherein the lubricating oil composition has a ratioof sulfur to molybdenum of less than or equal to about 4:1. In oneembodiment, the lubricating oil composition of the present invention hasa sulfur content of up to about 0.3 wt. %, and/or sulfated ash contentof up to about 0.4 wt. % as determined by ASTM D874. The amount ofsulfur, boron, molybdenum or phosphorus in the lubricating oilcomposition of the present invention is measured according to ASTMD4951.

The oil of lubricating viscosity for use in the lubricating oilcompositions of this invention, also referred to as a base oil, istypically present in a major amount, e.g., an amount of greater than 50wt. %, preferably greater than about 70 wt. %, more preferably fromabout 80 to about 99.5 wt. % and most preferably from about 80 to about98 wt. %, based on the total weight of the composition. The expression“base oil” as used herein shall be understood to mean a base stock orblend of base stocks which is a lubricant component that is produced bya single manufacturer to the same specifications (independent of feedsource or manufacturer's location); that meets the same manufacturer'sspecification; and that is identified by a unique formula, productidentification number, or both. The base oil for use herein can be anypresently known or later-discovered oil of lubricating viscosity used informulating lubricating oil compositions for any and all suchapplications, e.g., engine oils, marine cylinder oils, functional fluidssuch as hydraulic oils, gear oils, transmission fluids, etc. Forexample, the base oils can be used in formulating lubricating oilcompositions for any and all such applications such as passenger carengine oils, heavy duty diesel motor oils and natural gas engine oils.Additionally, the base oils for use herein can optionally containviscosity index, improvers, e.g., polymeric alkylmethacrylates; olefiniccopolymers, e.g., an ethylene-propylene copolymer or a styrene-butadienecopolymer; and the like and mixtures thereof.

As one skilled in the art would readily appreciate, the viscosity of thebase oil is dependent upon the application. Accordingly, the viscosityof a base oil for use herein will ordinarily range from about 2 to about2000 centistokes (cSt) at 100° Centigrade (C). Generally, individuallythe base oils used as engine oils will have a kinematic viscosity rangeat 100° C. of about 2 cSt to about 30 cSt, preferably about 3 cSt toabout 16 cSt, and most preferably about 4 cSt to about 12 cSt and willbe selected or blended depending on the desired end use and theadditives in the finished oil to give the desired grade of engine oil,e.g., a lubricating oil composition having an SAE Viscosity Grade of 0W,0W-20, 0W-30, 0W-40, 0W-50, 0W-60, 5W, 5W-20, 5W-30, 5W-40, 5W-50,5W-60, 10W, 10W-20, 10W-30, 10W-40, 10W-50, 15W, 15W-20, 15W-30 or15W-40. Oils used as gear oils can have viscosities ranging from about 2cSt to about 2000 cSt at 100° C.

Base stocks may be manufactured using a variety of different processesincluding, but not limited to, distillation, solvent refining, hydrogenprocessing, oligomerization, esterification, and rerefining. Rerefinedstock shall be substantially free from materials introduced throughmanufacturing, contamination, or previous use. The base oil of thelubricating oil compositions of this invention may be any natural orsynthetic lubricating base oil. Suitable hydrocarbon synthetic oilsinclude, but are not limited to, oils prepared from the polymerizationof ethylene or from the polymerization of 1-olefins to provide polymerssuch as polyalphaolefin or PAO oils, or from hydrocarbon synthesisprocedures using carbon monoxide and hydrogen gases such as in aFischer-Tropsch process. For example, a suitable base oil is one thatcomprises little, if any, heavy fraction; e.g., little, if any, lube oilfraction of viscosity 20 cSt or higher at 100° C.

The base oil may be derived from natural lubricating oils, syntheticlubricating oils or mixtures thereof. Suitable base oil includes basestocks obtained by isomerization of synthetic wax and slack wax, as wellas hydrocracked base stocks produced by hydrocracking (rather thansolvent extracting) the aromatic and polar components of the crude.Suitable base oils include those, in all API categories I, II, III, IVand V as defined in API Publication 1509, 14th Edition, Addendum I,December 1998. Group IV base oils are polyalphaolefins (PAO). Group Vbase oils include all other base oils not included in Group I, II, III,or IV. Although Group II, III and IV base oils are preferred for use inthis invention, these base oils may be prepared by combining one or moreof Group I, II, III, IV and V base stocks or base oils.

Useful natural oils include mineral lubricating oils such as, forexample, liquid petroleum oils, solvent-treated or acid-treated minerallubricating oils of the paraffinic, naphthenic or mixedparaffinic-naphthenic types, oils derived from coal or shale, animaloils, vegetable oils (e.g., rapeseed oils, castor oils and lard oil),and the like.

Useful synthetic lubricating oils include, but are not limited to,hydrocarbon oils and halo-substituted hydrocarbon oils such aspolymerized and interpolymerized olefins, e.g., polybutylenes,polypropylenes, propylene-isobutylene copolymers, chlorinatedpolybutylenes, poly(1-hexenes), poly(1-octenes), poly(1-decenes), andthe like and mixtures thereof, alkylbenzenes such as dodecylbenzenes,tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)-benzenes, and thelike, polyphenyls such as biphenyls, terphenyls, alkylated polyphenyls,and the like, alkylated diphenyl ethers and alkylated diphenyl sulfidesand the derivative, analogs and homologs thereof and the like.

Other useful synthetic lubricating oils include, but are not limited to,oils made by polymerizing olefins of less than 5 carbon atoms such asethylene, propylene, butylenes, isobutene, pentene, and mixturesthereof. Methods of preparing such polymer oils are well known to thoseskilled in the art.

Additional useful synthetic hydrocarbon oils include liquid polymers ofalpha olefins having the proper viscosity. Especially useful synthetichydrocarbon oils are the hydrogenated liquid oligomers of C₆ to C₁₂alpha olefins such as, for example, 1-decene trimer.

Another class of useful synthetic lubricating oils include, but are notlimited to, alkylene oxide polymers, i.e., homopolymers, interpolymers,and derivatives thereof where the terminal hydroxyl groups have beenmodified by, for example, esterification or etherification. These oilsare exemplified by the oils prepared through polymerization of ethyleneoxide or propylene oxide, the alkyl and phenyl ethers of thesepolyoxyalkylene polymers (e.g., methyl poly propylene glycol etherhaving an average molecular weight of 1,000, diphenyl ether ofpolyethylene glycol having a molecular weight of 500-1000, diethyl etherof polypropylene glycol having a molecular weight of 1,000-1,500, etc.)or mono- and polycarboxylic esters thereof such as, for example, theacetic esters, mixed C₃-C₈ fatty acid esters, or the C₁₃ oxo, aciddiester of tetraethylene glycol.

Yet another class of useful synthetic lubricating oils include, but arenot limited to, the esters of dicarboxylic acids e.g., phthalic acid,succinic acid, alkyl succinic acids, alkenyl succinic acids, maleicacid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipicacid, linoleic acid dimer, malonic acids, alkyl malonic acids, alkenylmalonic acids, etc., with a variety of alcohols, e.g., butyl alcohol,hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol,diethylene glycol monoether, propylene glycol, etc. Specific examples ofthese esters include dibutyl adipate, di(2-ethylhexyl)sebacate,di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecylazelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the2-ethylhexyl diester of linoleic acid dimer, the complex ester formed byreacting one mole of sebacic acid with two moles of tetraethylene glycoland two moles of 2-ethylhexanoic acid, and the like.

Esters useful as synthetic oils also include, but are not limited to,those made from carboxylic acids having from about 5 to about 12 carbonatoms with alcohols, e.g., methanol, ethanol, etc., polyols and polyolethers such as neopentyl glycol, trimethylol propane, pentaerythritol,dipentaerythritol, tripentaerythritol, and the like.

Silicon-based oils such as for example, polyalkyl-, polyaryl-,polyalkoxy- or polyaryloxy-siloxane oils and silicate oils, compriseanother useful class of synthetic lubricating oils. Specific examples ofthese include, but are not limited to, tetraethyl silicate,tetra-isopropyl silicate, tetra-(2-ethylhexyl) silicate,tetra-(4-methyl-hexyl)silicate, tetra-(p-tert-butylphenyl)silicate,hexyl-(4-methyl-2-pentoxy)disiloxane, poly(methyl)siloxanes,poly(methylphenyl)siloxanes, and the like. Still yet other usefulsynthetic lubricating oils include, but are not limited to liquid estersof phosphorus containing acids, e.g., tricresyl phosphate, trioctylphosphate, diethyl ester of decane phosphionic acid, etc., polymerictetrahydrofurans, and the like.

The lubricating oil may be derived from unrefined, refined and rerefinedoils, either natural, synthetic or mixtures of two or more of any ofthese of the type disclosed hereinabove. Unrefined oils are thoseobtained directly from a natural or synthetic source (e.g., coal, shale,or tar sands bitumen) without further purification or treatment.Examples of unrefined oils include, but are not limited to, a shale oilobtained directly from retorting operations, a petroleum oil obtaineddirectly from distillation or an ester oil obtained directly from anesterification process, each of which is then used without furthertreatment. Refined oils are similar to the unrefined oils except theyhave been further treated in one or more purification steps to improveone or more properties. These purification techniques are known to thoseof skill in the art and include, for example, solvent extractions,secondary distillation, acid or base extraction, filtration,percolation, hydrotreating, dewaxing, etc. Rerefined oils are obtainedby treating used oils in processes similar to those used to obtainrefined oils. Such rerefined oils are also known as reclaimed orreprocessed oils and often are additionally processed by techniquesdirected to removal of spent additives and oil breakdown products.

Lubricating oil base stocks derived from the hydroisomerization of waxmay also be used, either alone or in combination with the aforesaidnatural and/or synthetic base stocks. Such wax isomerate oil is producedby the hydroisomerization of natural or synthetic waxes or mixturesthereof over a hydroisomerization catalyst.

Natural waxes are typically the slack waxes recovered by the solventdewaxing of mineral oils; synthetic waxes are typically the wax producedby the Fischer-Tropsch process.

The Oil-Soluble or Dispersed Oil-Stable Boron-Containing Compound

Representative examples of at least one oil-soluble or dispersedoil-stable boron-containing compound for use in the lubricating oilcompositions of the present invention include a borated dispersant; aborated friction modifier; a dispersed alkali metal or a mixed alkalimetal or an alkaline earth metal borate, a borated epoxide, a borateester, a borated fatty amine, a borated amide, a borated sulfonate, andthe like, and mixtures thereof.

Examples of borated dispersants include, but are not limited to, boratedashless dispersants such as the borated polyalkenyl succinic anhydrides;borated non-nitrogen containing derivatives of a polyalkylene succinicanhydride; a borated basic nitrogen compound selected from the groupconsisting of succinimides, carboxylic acid amides, hydrocarbylmonoamines, hydrocarbyl polyamines, Mannich bases, phosphonoamides,thiophosphonamides and phosphoramides, thiazoles, e.g.,2,5-dimercapto-1,3,4-thiadiazoles, mercaptobenzothiazoles andderivatives thereof, triazoles, e.g., alkyltriazoles and benzotriazoles,copolymers which contain a carboxylate ester with one or more additionalpolar function, including amine, amide, imine, imide, hydroxyl,carboxyl, and the like, e.g., products prepared by copolymerization oflong chain alkyl acrylates or methacrylates with monomers of the abovefunction; and the like and mixtures thereof. A preferred borateddispersant is a succinimide derivative of boron such as, for example, aborated polyisobutenyl succinimide.

Examples of borated friction modifiers include, but are not limited to,borated fatty epoxides, borated alkoxylated fatty amines, boratedglycerol esters and the like and mixtures thereof.

The hydrated particulate alkali metal borates are well known in the artand are available commercially. Representative examples of hydratedparticulate alkali metal borates and methods of manufacture includethose disclosed in, e.g., U.S. Pat. Nos. 3,313,727; 3,819,521;3,853,772; 3,907,601; 3,997,454; 4,089,790; 6,737,387 and 6,534,450, thecontents of which are incorporated herein by reference. The hydratedalkali metal borates can be represented by the following Formula:M₂O.mB₂O₃.nH₂O where M is an alkali metal of atomic number in the rangeof about 11 to about 19, e.g., sodium and potassium; m is a number fromabout 2.5 to about 4.5 (both whole and fractional); and n is a numberfrom about 1.0 to about 4.8. Preferred are the hydrated sodium borates.The hydrated borate particles generally have a mean particle size ofless than about 1 micron.

Examples of borated epoxides include borated epoxides obtained from thereaction product of one or more of the boron compounds with at least oneepoxide. Suitable boron compounds include boron oxide, boron oxidehydrate, boron trioxide, boron trifluoride, boron tribromide, borontrichloride, boron acids such as boronic acid, boric acid, tetraboricacid and metaboric acid, boron amides and various esters of boron acids.The epoxide is generally an aliphatic epoxide having from about 8 toabout 30 carbon atoms and preferably from about 10 to about 24 carbonatoms and more preferably from about 12 to about 20 carbon atoms.Suitable aliphatic epoxides include dodecene oxide, hexadecene oxide andthe like and mixtures thereof. Mixtures of epoxides may also be used,for instance commercial mixtures of epoxides having from about 14 toabout 16 carbon atoms or from about 14 to about 18 carbon atoms. Theborated epoxides are generally known and described in, for example, U.S.Pat. No. 4,584,115.

Examples of borate esters include those borate esters obtained byreacting one or more of the boron compounds disclosed above with one ormore alcohols of suitable oleophilicity. Typically, the alcohols willcontain from 6 to about 30 carbons and preferably from 8 to about 24carbon atoms. The methods of making such borate esters are well known inthe art. The borate esters can also be borated phospholipids.Representative examples of borate esters include those having thestructures set forth in Formulae I-III:

wherein each R is independently a C₁-C₁₂ straight or branched alkylgroup and R¹ is hydrogen or a C₁-C₁₂ straight or branched alkyl group.

Examples of borated fatty amines include borated fatty amines obtainedby reacting one or more of the boron compounds disclosed above with oneor more of fatty amines, e.g., an amine having from about fourteen toabout eighteen carbon atoms. The borated fatty amines may be prepared byreacting the amine with the boron compound at a temperature in the rangeof from about 50 to about 300° C., and preferably from about 100 toabout 250° C., and at a ratio from about 3:1 to about 1:3 equivalents ofamine to equivalents of boron compound.

Examples of borated amides include borated amides obtained from thereaction product of a linear or branched, saturated or unsaturatedmonovalent aliphatic acid having 8 to about 22 carbon atoms, urea, andpolyalkylenepolyamine with a boric acid compound and the like andmixtures thereof.

Examples of borated sulfonates include borated alkaline earth metalsulfonates obtained by (a) reacting in the presence of a hydrocarbonsolvent (i) at least one of an oil-soluble sulfonic acid or alkalineearth sulfonate salt or mixtures thereof; (ii) at least one source of analkaline earth metal; (iii) at least one source of boron, and (iv) from0 to less than 10 mole percent, relative to the source of boron, of anoverbasing acid, other than the source of boron; and (b) heating thereaction product of (a) to a temperature above the distillationtemperature of the hydrocarbon solvent to distill the hydrocarbonsolvent and water from the reaction. Suitable borated alkaline earthmetal sulfonates include those disclosed in, for example, U.S. PatentApplication Publication No. 20070123437, the contents of which areincorporated by reference herein.

The lubricating oil compositions of the present invention will containno more than about 400 ppm of boron, based upon the total mass of thecomposition, provided from the one or more oil-soluble or dispersedoil-stable boron-containing compounds. In one embodiment, thelubricating oil compositions of the present invention will contain nomore than about 300 ppm of boron, based upon the total mass of thecomposition, provided from the one or more oil-soluble or dispersedoil-stable boron-containing compounds. In another embodiment, thelubricating oil compositions of the present invention will contain nomore than about 200 ppm of boron, based upon the total mass of thecomposition, provided from the one or more oil-soluble or dispersedoil-stable boron-containing compounds. In yet another embodiment, thelubricating oil compositions of the present invention will contain nomore than about 100 ppm of boron, based upon the total mass of thecomposition, provided from the one or more oil-soluble or dispersedoil-stable boron-containing compounds. In another embodiment, thelubricating oil compositions of the present invention will contain fromabout 40 ppm to no more than about 400 ppm of boron, based upon thetotal mass of the composition, provided from the one or more oil-solubleor dispersed oil-stable boron-containing compounds. In still yet anotherembodiment, the lubricating oil compositions of the present inventionwill be substantially free of any boron content.

The Oil-Soluble or Dispersed Oil-Stable Molybdenum-Containing Compound

Representative examples of at least one oil-soluble or dispersedoil-stable molybdenum-containing compound for use in the lubricating oilcompositions of the present invention include molybdenumdithiocarbamates; molybdenum dithiophosphates; dispersed hydratedmolybdenum compounds; acidic molybdenum compounds or salts of acidicmolybdenum compounds; molybdenum-containing complexes and the like andmixtures thereof.

Examples of dispersed hydrated molybdenum, compounds include dispersedhydrated polymolybdates, dispersed hydrated alkali metal polymolybdatesand the like and mixtures thereof. Suitable dispersed hydratedpolymolybdates include those disclosed in, for example, U.S. PatentApplication Publication No. 20050070445, the contents of which areincorporated by reference herein.

Suitable molybdenum dithiocarbamates include any molybdenumdithiocarbamate which can be used as an additive for lubricating oils.One class of molybdenum dithiocarbamates for use herein is representedby Formula IV:

wherein R², R³, R⁴, and R⁵ are each independently: hydrogen or ahydrocarbon group including, by way of example, alkyl groups, alkenylgroups, aryl groups, cycloalkyl groups and cycloalkenyl groups, and X¹,X², X³ and X⁴ are each independently sulfur or oxygen.

Suitable alkyl groups include, but are not limited to, methyl, ethyl,propyl, isopropyl, butyl, isobutyl, secondary butyl, tertiary butyl,pentyl, isopentyl, secondary pentyl, neopentyl, tertiary pentyl, hexyl,secondary hexyl, heptyl, secondary heptyl, octyl, 2-ethylhexyl,secondary octyl, nonyl, secondary nonyl, decyl, secondary decyl,undecyl, secondary undecyl, dodecyl, secondary dodecyl, tridecyl,isotridecyl, secondary tridecyl, tetradecyl, secondary tetradecyl,hexadecyl, secondary hexadecyl, stearyl, icosyl, docosyl, tetracosyl,triacontyl, 2-butyloctyl, 2-butyldecyl, 2-hexyloctyl, 2-hexyldecyl,2-octyldecyl, 2-hexyldodecyl, 2-octyldodecyl, 2-decyltetradecyl,2-dodecylhexadecyl, 2-hexadecyloctadecyl, 2-tetradecyloctadecyl,monomethyl branched-isostearyl and the like.

Suitable alkenyl groups include, but are not limited to, vinyl, allyl,propenyl, butenyl, isobutenyl, pentenyl, isopentenyl, hexenyl, heptenyl,octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tetradecenyl, oleyl andthe like.

Suitable aryl groups include, but are not limited to, phenyl, tolyl,xylyl, cumenyl, mesityl, benzyl, phenethyl, styryl, cinnamyl,benzhydryl, trityl, ethylphenyl, propylphenyl, butylphenyl,pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl,decylphenyl, undecylphenyl, dodecylphenyl, biphenyl, benzylphenyl,styrenated phenyl, p-cumylphenyl, alpha-naphthyl, beta-naphthyl groupsand the like.

Suitable cycloalkyl groups and cycloalkenyl groups include, but are notlimited to, cyclopentyl, cyclohexyl, cycloheptyl, methylcyclopentyl,methylcyclohexyl, methylcycloheptyl, cyclopentenyl, cyclohexenyl,cycloheptenyl, methylcyclopentenyl, methylcyclohexenyl,methylcycloheptenyl groups and the like.

Of these groups, the alkyl groups or alkenyl groups are preferred as R²to R⁵ in Formula IV. Preferably, the R groups in Formula IV areidentical groups.

In Formula IV, X¹ to X⁴ are independently selected from sulfur or oxygenatom, and all of X¹ to X⁴ may be a sulfur atom or an oxygen atom, or amixture of sulfur atoms and oxygen atoms. In consideration of balancebetween friction reducing effect and corrosivity, the molar ratio (ratioof numbers) of sulfur atom(s)/oxygen atom(s) should particularlypreferably be in the range from about 1/3 to about 3/1.

Some of the oil-soluble or dispersed oil-stable molybdenum compounds ofFormula IV are commercially available. For example, products where X¹and X² are O, X³ and X⁴ are S, and where R² to R⁵ are C₁₃H₂₇ aliphatichydrocarbyl groups and where the molybdenum is in oxidation state V aresold under the trademarks Molyvan 807 and Molyvan 822 as antioxidantsand friction reducing additives by R.T. Vanderbilt Company Inc.(Norwalk, Conn. USA). These molybdenum compounds may be prepared by themethods described in U.S. Pat. No. 3,356,702 wherein MoO₃ is convertedto soluble molybdate by dissolving in alkali metal hydroxide solution,neutralized by the addition of acid followed by the addition of asecondary amine and carbon disulfide. In another aspect, the molybdenumcompounds of Formula I wherein X¹ to X⁴ are O or S may be prepared by anumber of methods known in the art such as, for example, U.S. Pat. Nos.4,098,705 and 5,631,213.

Generally, the sulfurized oxymolybdenum dithiocarbamates represented byFormula IV can be prepared by reacting molybdenum trioxide or amolybdate with an alkali sulfide or an alkali hydrosulfide, andsubsequently, adding carbon disulfide and a secondary amine to thereaction mixture and reacting the resultant mixture at an adequatetemperature. To prepare the asymmetric sulfurized oxymolybdenumdithiocarbamates, the use of a secondary amine having differenthydrocarbon groups or the use of two or more different secondary aminesin the above process is sufficient. The symmetric sulfurizedoxymolybdenum dithiocarbamates can also be prepared in a similar manner,but with the use of only one secondary amine.

Examples of suitable molybdenum dithiocarbamate compounds include, butare not limited to, sulfurized molybdenum diethyldithiocarbamate,sulfurized molybdenum dipropyldithiocarbamate, sulfurized molybdenumdibutyldithiocarbamate, sulfurized molybdenum dipentyldithiocarbamate,sulfurized molybdenum dihexyldithiocarbamate, sulfurized molybdenumdioctyldithiocarbamate, sulfurized molybdenum didecyldithiocarbamate,sulfurized molybdenum didodecyldithiocarbamate, sulfurized molybdenumditridecyldithiocarbamate, sulfurized molybdenumdi(butylphenyl)dithiocarbamate, sulfurized molybdenumdi(nonylphenyl)dithiocarbamate, sulfurized oxymolybdenumdiethyldithiocarbamate, sulfurized oxymolybdenumdipropyldithiocarbamate, sulfurized oxymolybdenumdibutyldithiocarbamate, sulfurized oxymolybdenumdipentyldithiocarbamate, sulfurized oxymolybdenumdihexyldithiocarbamate, sulfurized oxymolybdenum dioctyldithiocarbamate,sulfurized oxymolybdenum didecyldithiocarbamate, sulfurizedoxymolybdenum didodecyldithiocarbamate, sulfurized oxymolybdenumditridecyldithiocarbamate, sulfurized oxymolybdenumdi(butylphenyl)dithiocarbamate, sulfurized oxymolybdenumdi(nonylphenyl)dithiocarbamate, all of which the alkyl groups may bestraight-chain or branched, and the like and mixtures thereof.

Suitable molybdenum dithiophosphates include any molybdenumdithiophosphate which can be used as an additive for lubricating oils.Examples of suitable molybdenum dithiophosphates include molybdenumdialkyl or diaryl dithiophosphate such as molybdenumdiisopropyldithiophosphate, molybdenum di-(2-ethylhexyl)dithiophosphate,molybdenum di-(nonylphenyl)dithiophosphate and the like and mixturesthereof.

The molybdenum-containing complexes may be generally characterized ascontaining a molybdenum or molybdenum/sulfur complex of a basic nitrogencompound. The molybdenum/nitrogen-containing complexes employed hereinare well known in the art and are complexes of molybdic acid and anoil-soluble basic nitrogen-containing compound. Generally, themolybdenum/nitrogen-containing complex can be made with an organicsolvent comprising a polar promoter during a complexation step andprocedures for preparing such complexes are described, for example, inU.S. Pat. Nos. 4,259,194; 4,259,195; 4,261,843; 4,263,152; 4,265,773;4,283,295; 4,285,822; 4,369,119; 4,370,246; 4,394,279; 4,402,840; and6,962,896 and U.S. Patent Application Publication No. 2005/0209111. Asshown in these references the molybdenum/nitrogen-containing complex canfurther be sulfurized.

In another embodiment, a molybdated succinimide complex can be preparedby a process which involves at least (a) reacting an alkyl or alkenylsuccinimide of a polyamine of Formula V:

wherein R⁶ is an about C₁₂ to about C₃₀ alkyl or alkenyl group; a and bare independently 2 or 3, and x is 0 to 10, preferably 1 to 6 and morepreferably 2 to 5; with an ethylenically unsaturated carboxylic acidand/or anhydride thereof; and (b) reacting the succinimide product ofstep (a) with an acidic molybdenum compound, e.g., as disclosed in U.S.patent application Ser. No. 12/215,723, filed on Jun. 30, 2008, thecontents of which are incorporated by reference herein. In oneembodiment, the R⁶ substituent has a number average molecular weightranging from about 167 to about 419 and preferably from about 223 toabout 279. In another embodiment, R⁶ is an about C₁₂ to about C₂₄ alkylor alkenyl group; a and b are each 2; and x is 2 to 5.

In step (a), a succinimide of Formula V:

wherein R⁶, a, b and x have the aforestated meanings, is reacted with anethylenically unsaturated carboxylic acid. The starting succinimide ofFormula V can be obtained by reacting an anhydride of Formula VI:

wherein R⁶ has the aforestated meaning with a polyamine. The anhydrideof Formula VI is either commercially available from such sources as, forexample, Sigma Aldrich Corporation (St. Louis, Mo., U.S.A.), or can beprepared by any method well known in the art.

Suitable polyamines for use in preparing the succinimide of Formula Vare polyalkylene polyamines, including polyalkylene diamines. Suchpolyalkylene polyamines will typically contain about 2 to about 12nitrogen atoms and about 2 to 24 carbon atoms. Particularly suitablepolyalkylene polyamines are those having the Formula: H₂N—(R⁷NH)_(c)—Hwherein R⁷ is a straight- or branched-chain alkylene group having 2 or 3carbon atoms and c is 1 to 9. Representative examples of suitablepolyalkylene polyamines include ethylenediamine, diethylenetriamine,triethylenetetraamine, tetraethylenepentamine, and mixtures thereof.Most preferably, the polyalkylene polyamine is tetraethylenepentamine.

Many of the polyamines suitable for use in the present invention arecommercially available and others may be prepared by methods which arewell known in the art. For example, methods for preparing amines andtheir reactions are detailed in Sidgewick's “The Organic Chemistry ofNitrogen”, Clarendon Press, Oxford, 1966; Noller's “Chemistry of OrganicCompounds”, Saunders, Philadelphia, 2nd Ed., 1957; and Kirk-Othmer's“Encyclopedia of Chemical Technology”, 2nd Ed., especially Volume 2, pp.99-116.

Generally, the anhydride of Formula VI is reacted with the polyamine ata temperature of about 130° C. to about 220° C. and preferably fromabout 145° C. to about 175° C. The reaction can be carried out under aninert atmosphere, such as nitrogen or argon. The amount of anhydride ofFormula VI employed in the reaction can range from about 30 to about 95wt. % and preferably from about 40 to about 60 wt. %, based on the totalweight of the reaction mixture.

Suitable ethylenically unsaturated carboxylic acids or their anhydridesinclude ethylenically unsaturated monocarboxylic acids or theiranhydrides, ethylenically unsaturated dicarboxylic acids or theiranhydrides and the like and mixtures thereof. Useful monocarboxylicacids or their anhydrides include, but are not limited to, acrylic acid,methacrylic acid, and the like and mixtures thereof. Usefulethylenically unsaturated dicarboxylic acids or their anhydridesinclude, but are not limited to, fumaric acid, maleic anhydride,mesaconic acid, citraconic acid, citraconic anhydride, itaconic acid,itaconic anhydride, and the like and mixtures thereof. A preferredethylenically unsaturated carboxylic acid or anhydride thereof is maleicanhydride or a derivative thereof. This and similar anhydrides bond ontothe succinimide starting compound to provide a carboxylic acidfunctionality. The treatment of the succinimide of Formula V with theethylenically unsaturated carboxylic acid or anhydrides thereofadvantageously allows for a sufficient amount of the molybdenum compoundto be incorporated into the complex.

Generally, the ethylenically unsaturated carboxylic acid or itsanhydride is heated to a molten condition at a temperature in the rangeof from about 50° C. to about 100° C. and is thereafter mixed with thesuccinimide of Formula V. The molar ratio of ethylenically unsaturatedcarboxylic acid or its anhydride to succinimide of Formula V will varywidely, e.g., a range of from about 0.1:1 to about 2:1. In oneembodiment, the charge molar ratio of ethylenically unsaturatedcarboxylic acid or its anhydride to succinimide of Formula V will rangeof from about 0.9:1 to about 1.05:1.

The molybdenum compounds used to prepare the molybdated succinimidecomplex of the present invention are acidic molybdenum compounds orsalts of acidic molybdenum compounds. Generally, these molybdenumcompounds are hexavalent. Representative examples of suitable molybdenumcompounds can be any of the acid molybdenum compounds discussed above.Particularly preferred is molybdenum trioxide.

In step (b), a mixture of the succinimide product of step (a) and acidicmolybdenum compound is prepared with or without a diluent. A diluent isused, if necessary, to provide a suitable viscosity for stirring.Suitable diluents are lubricating oils and liquid compounds containingonly carbon and hydrogen. If desired, ammonium hydroxide may also beadded to the reaction mixture to provide a solution of ammoniummolybdate.

Generally, the reaction mixture is heated at a temperature less than orequal to about 100° C. and preferably from about 80° C. to about 100° C.until the molybdenum is sufficiently reacted. The reaction time for thisstep is typically in the range of about 15 minutes to about 5 hours andpreferably about 1 to about 2 hours. The molar ratio of the molybdenumcompound to the succinimide product of step (a) is about 0.1:1 to about2:1, preferably from about 0.5:1 to about 1.5:1 and most preferablyabout 1:1. Any water present following the reaction of the molybdenumcompound and succinimide product of step (a) can be removed by heatingthe reaction mixture to a temperature greater than about 100° C., andpreferably from about 120° C. to about 160° C.

In another embodiment, a molybdated succinimide complex can be preparedby a process which involves at least (a) reacting a succinimide of apolyamine of Formula VII:

wherein R⁸ is a hydrocarbon radical having a number average molecularweight of about 500 to about 5,000; preferably a number averagemolecular weight of about 700 to about 2,500 and more preferably anumber average molecular weight of about 710 to about 1,100; a and b areindependently 2 or 3; and x is 0 to 10, preferably 1 to 6 and morepreferably 2 to 5, with an ethylenically unsaturated carboxylic acid oranhydride thereof, in a charge mole ratio of the ethylenicallyunsaturated carboxylic acid or anhydride thereof to the succinimide ofFormula VII of about 0.9:1 to about 1.05:1; and (b) reacting thesuccinimide product of step (a) with an acidic molybdenum compound,e.g., as disclosed in U.S. patent application Ser. No. 12/215,739, filedon Jun. 30, 2008, the contents of which are incorporated by referenceherein. In one embodiment, R⁸ is an alkyl or alkenyl group. In anotherembodiment, R⁸ is a polyalkenyl group. A preferred polyalkenyl group isa polyisobutenyl group.

In step (a), a succinimide of Formula VII:

wherein R⁸, a, b and x have the aforestated meanings, is reacted with anethylenically unsaturated carboxylic-acid in a charge mole ratio of theethylenically unsaturated carboxylic acid or anhydride thereof to thesuccinimide of Formula I of about 0.9:1 to about 1.05:1. The startingsuccinimide of Formula VII can be obtained by reacting an anhydride ofFormula VIII:

wherein R⁸ has the aforestated meaning with a polyamine. The anhydrideof Formula VIII is either commercially available from such sources as,for example, Sigma Aldrich Corporation (St. Louis, Mo., U.S.A.), or canbe prepared by any method well known in the art.

Suitable polyamines for use in preparing the succinimide of Formula VIIcan be any of the polyamines disclosed herein above for making thesuccinimide of Formula V. Preferably, the polyalkylene polyamine istetraethylenepentamine.

Generally, the anhydride of Formula VIII is reacted with the polyamineat a temperature of about 130° C. to about 220° C. and preferably fromabout 145° C. to about 175° C. The reaction can be carried out under aninert atmosphere, such as nitrogen or argon. The amount of anhydride ofFormula VIII employed in the reaction can range from about 30 to about95 wt % and preferably from about 40 to about 60 wt %, based on, thetotal weight of the reaction mixture.

Suitable ethylenically unsaturated carboxylic acids or their anhydridescan be any of the ethylenically unsaturated carboxylic acids or theiranhydrides disclosed hereinabove for making the molybdated succinimidecomplex employing the succinimide of Formula V. A preferredethylenically unsaturated carboxylic acid or anhydride thereof is maleicanhydride or a derivative thereof.

Generally, the ethylenically unsaturated carboxylic acid or anhydridethereof is heated to a molten condition at a temperature in the range offrom about 50° C. to about 100° C. and is thereafter mixed with thesuccinimide of Formula VII.

The molybdenum compounds used to prepare the molybdated succinimidecomplex can be any of the molybdenum compounds disclosed herein abovefor making the molybdated succinimide complex employing the succinimideof Formula V. Particularly preferred is molybdenum trioxide.

In step (b), a mixture of, the succinimide product of step (a) andacidic molybdenum compound is prepared with or without a diluent. Adiluent is used, if necessary, to provide a suitable viscosity for easystirring. Suitable diluents are lubricating oils and liquid compoundscontaining only carbon and hydrogen. If desired, ammonium hydroxide mayalso be added to the reaction mixture to provide a solution of ammoniummolybdate

Generally, the reaction mixture is heated at a temperature less than orequal to about 100° C. and preferably from about 80° C. to about 100° C.until the molybdenum is sufficiently reacted. The reaction time for thisstep is typically in the range of about 15 minutes to about 5 hours andpreferably about 1 to about 2 hours. The molar ratio of the molybdenumcompound to the succinimide product of step (a) is about 0.1:1 to about2:1, preferably from about 0.5:1 to about 1.5:1 and most preferablyabout 1:1. Any water present following the reaction of the molybdenumcompound and succinimide product of step (a) can be removed by heatingthe reaction mixture to a temperature greater than about 100° C., andpreferably from about 120° C. to about 160° C.

The lubricating oil compositions of the present invention will containat least about 1100 ppm of molybdenum, based upon the total mass of thecomposition, provided from the one or more oil-soluble or dispersedoil-stable molybdenum-containing compounds. In one embodiment, thelubricating oil compositions of the present invention will contain about1100 ppm to about 2000 ppm of molybdenum, based upon the total mass ofthe composition, provided from the one or more oil-soluble or dispersedoil-stable molybdenum-containing compounds.

In one embodiment, the oil-soluble or dispersed oil-stablemolybdenum-containing compound will be present in the lubricating oilcomposition of the present invention such that the lubricating oilcomposition has a ratio of sulfur to molybdenum of less than or equal toabout 4:1. In another embodiment, the lubricating oil composition has aratio of sulfur to molybdenum of less than about 3:1. In yet anotherembodiment, the lubricating oil composition has a ratio of sulfur tomolybdenum of about 0.5:1 to about 4:1. In another embodiment, thelubricating oil composition has a ratio of sulfur to molybdenum of about1:1 to about 4:1. In still another embodiment, the lubricating oilcomposition has a ratio of sulfur to molybdenum of about 1:1 to about3:1. In still yet another embodiment, the lubricating oil compositionhas a ratio of sulfur to molybdenum of about 1:1 to about 2.5:1.

The lubricating oil compositions of the present invention will have asulfur content of up to about 0.4 wt. % and preferably up to about 0.3wt. %. The sulfur content can be derived from elemental sulfur or asulfur-containing compound. The sulfur or sulfur-containing compound maybe intentionally added to the lubricating oil composition, or it may bepresent in the base oil or in one or more of the additives for thelubricating oil composition. In one embodiment, a major amount of thesulfur in the lubricating oil composition is derived from an activesulfur compound, i.e., an amount greater than 50%. By “active sulfur” ismeant a sulfur compound which is antiwear active and preferablyanticorrosive. The sulfur-containing compound may be an inorganic sulfurcompound or an organic sulfur compound. The sulfur-containing compoundmay be a compound containing one or more of the groups: sulfamoyl,sulfenamoyl, sulfeno, sulfido, sulfinamoyl, sulfino, sulfonyl, sulfo,sulfonio, sulfonyl, sulfonyldioxy, sulfate, thio, thiocarbamoyl,thiocarbonyl, thiocarbonylamino, thiocarboxy, thiocyanato, thioformyl,thioxo, thioketone, thioaldehyde, thioester, and the like. The sulfurmay also be present in a hetero group or compound which contains carbonatoms and sulfur atoms (and, optionally, other hetero atoms such asoxygen or nitrogen) in a chain or ring. Preferred sulfur-containingcompounds include dihydrocarbyl sulfides and polysulfides such as alkylor alkenyl sulfides and polysulfides, sulfurized fatty acids or estersthereof, ashless dithiophosphates, cyclic organo-sulfur compounds,polyisobutyl thiothione compounds, ashless dithiocarbamates and mixturesthereof.

Examples of the dihydrocarbyl sulfides or polysulfides include compoundsrepresented by Formula VIII:

R⁹—S_(b)—R¹⁰  (VIII)

wherein R⁹ and R¹⁰ are the same or different and represent a C₁ to C₁₀alkyl group, alkenyl group or a cyclic alkyl group, a C₆ to C₂₀ arylgroup, a C₇ to C₂₀ alkyl aryl group, or a C₇ to C₂₀ aryl alkyl group;and b is an integer of 1 to 7. When each of R⁹ and R¹⁰ is an alkylgroup, the compound is called an alkyl sulfide. Examples of the grouprepresented by R⁹ and R¹⁰ in Formula VIII include methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentylgroups, hexyl groups, heptyl groups, octyl groups, nonyl groups, decylgroups, dodecyl groups, cyclohexyl, phenyl, naphthyl, tolyl, xylyl,benzyl, and phenethyl.

One method of preparing the aromatic and alkyl sulfides includes thecondensation of a chlorinated hydrocarbon with an inorganic sulfidewhereby the chlorine atom from each of two molecules is displaced, andthe free valence from each molecule is joined to a divalent sulfur atom.Generally, the reaction is conducted in the presence of elementalsulfur.

Examples of alkenyl sulfides are described, for example, in U.S. Pat.No. 2,446,072. These sulfides can be prepared by interacting an olefinichydrocarbon containing from 3 to 12 carbon atoms with elemental sulfurin the presence of zinc or a similar metal generally in the form of anacid salt. Representative examples of alkenyl sulfides include6,6′-dithiobis(5-methyl-4-nonene), 2-butenyl monosulfide and disulfide,2-methyl-2-butenyl monosulfide and disulfide and the like.

The sulfurized fatty acid or ester thereof can be prepared by reacting,for example, sulfur, sulfur monochloride, and/or sulfur dichloride withan unsaturated fatty acid or ester thereof under elevated temperatures.Suitable fatty acids include C₈ to C₂₄ unsaturated fatty acids such as,for example, palmitoleic acid, oleic acid, ricinoleic acid, petroselinicacid, vaccenic acid, linoleic acid, linolenic acid, oleostearic acid,licanic acid, paranaric acid, tariric acid, gadoleic acid, arachidonicacid, cetoleic acid and the like. Also useful are mixed unsaturatedfatty acid, such as animal fats and vegetable oils, e.g., tall oil,linseed oil, olive oil, castor oil, peanut oil, rape oil, fish oil,sperm oil, and the like. Suitable fatty acid esters include C₁ to C₂₀alkyl esters of the foregoing fatty acids. Exemplary fatty estersinclude lauryl tallate, methyl oleate, ethyl oleate, lauryl oleate,cetyl oleate, cetyl linoleate, lauryl ricinoleate, oleyl linoleate,oleyl stearate, alkyl glycerides and the like.

One class of suitable ashless dithiophosphates for use herein includethose of the Formula IX:

wherein R¹¹ and R¹² are independently an alkyl group having 3 to 8carbon atoms (commercially available as VANLUBE® 7611M, from R.T.Vanderbilt Co., Inc.).

Another class of suitable ashless dithiophosphates for use hereininclude dithiophosphoric acid esters of carboxylic acid such as thosecommercially available as IRGALUBE® 63 from Ciba Geigy Corp.

Yet another class of suitable ashless dithiophosphates for use hereininclude triphenylphosphorothionates such as those commercially availableas IRGALUBE® TPPT from Ciba Geigy Corp.

Suitable polyisobutyl thiothione compounds include those compoundsrepresented by Formula X:

wherein R¹³ is hydrogen or methyl; X is sulfur or oxygen; m is aninteger from 1 to 9; and n is 0 or 1, and when n is 0 then R¹³ ismethyl, and when n is 1 then R¹³ is hydrogen. Examples of thesepolyisobutyl thiothione compounds are disclosed, in, for example, U.S.Patent Application Publication No. 20050153850, the contents of whichare incorporated by reference herein.

In a preferred embodiment, a sulfur compound for use in the lubricatingoil composition of the present invention is a bisdithiocarbamatecompound of Formula XI:

wherein R¹³, R¹⁴, R¹⁵, and R¹⁶ are the same or different and arealiphatic hydrocarbyl groups having 1 to 13 carbon atoms and R¹⁷ is analkylene group having 1 to 8 carbon atoms. The bisdithiocarbamates ofFormula XI are known compounds and described in U.S. Pat. No. 4,648,985incorporated herein by reference. The aliphatic hydrocarbyl groupshaving 1 to 13 carbon atoms can be branched or straight chain alkylgroups having 1 to 13 carbon atoms. A preferred bisdithiocarbamatecompound for use herein is methylenebis(dibutyldithiocarbamate)available commercially under the trademark Vanlube° 7723 (R. T.Vanderbilt Co., Inc.).

The lubricating oil compositions of the present invention can besubstantially free of any phosphorus content. In one embodiment, thelubricating oil compositions of the present invention are substantiallyfree of any zinc dialkyl dithiophosphate.

The lubricating oil compositions of the present invention may alsocontain other conventional additives for imparting auxiliary functionsto give a finished lubricating oil composition in which these additivesare dispersed or dissolved. For example, the lubricating oilcompositions can be blended with antioxidants, anti-wear agents,detergents such as metal detergents, rust inhibitors, dehazing agents,demulsifying agents, metal deactivating agents, friction modifiers, pourpoint depressants, antifoaming agents, co-solvents, packagecompatibilisers, corrosion-inhibitors, ashless dispersants, dyes,extreme pressure agents, and the like and mixtures thereof. A variety ofthe additives are known and commercially available. These additives, ortheir analogous compounds, can be employed for the preparation of thelubricating oil compositions of the invention by the usual blendingprocedures.

Examples of antioxidants include, but are not limited to, aminic types,e.g., diphenylamine, phenyl-alpha-napthyl-amine,N,N-di(alkylphenyl)amines; and alkylated phenylene-diamines; phenolicssuch as, for example, BHT, sterically hindered alkyl phenols such as2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, and2,6-di-tert-butyl-4-(2-octyl-3-propanoic) phenol; and mixtures thereof.

Examples of ashless dispersants include, but are not limited to,polyalkylene succinic anhydrides; non-nitrogen containing derivatives ofa polyalkylene succinic anhydride; a basic nitrogen compound selectedfrom the group consisting of succinimides, carboxylic acid amides,hydrocarbyl monoamines, hydrocarbyl polyamines, Mannich bases,phosphonoamides, and phosphoramides; triazoles, e.g., alkyltriazoles andbenzotriazoles; copolymers which contain a carboxylate ester with one ormore additional polar function, including amine, amide, imine, imide,hydroxyl, carboxyl, and the like, e.g., products prepared bycopolymerization of long chain alkyl acrylates or methacrylates withmonomers of the above function, and the like and mixtures thereof.

Examples of rust inhibitors include, but are not limited to, nonionicpolyoxyalkylene agents, e.g., polyoxyethylene lauryl ether,polyoxyethylene higher alcohol ether, polyoxyethylene nonylphenyl ether,polyoxyethylene octylphenyl ether, polyoxyethylene octyl stearyl ether,polyoxyethylene oleyl ether, polyoxyethylene sorbitol monostearate,polyoxyethylene sorbitol monooleate, and polyethylene glycol monooleate;stearic acid and other fatty acids; dicarboxylic acids; metal soaps;fatty acid amine salts; metal salts of heavy sulfonic acid; partialcarboxylic acid ester of polyhydric alcohol; phosphoric esters;(short-chain) alkenyl succinic acids; partial esters thereof andnitrogen-containing derivatives thereof; synthetic alkarylsulfonates,e.g., metal dinonylnaphthalene sulfonates; and the like and mixturesthereof.

Examples of friction modifiers include, but are not limited to,alkoxylated fatty amines; fatty phosphites, fatty epoxides, fattyamines, metal salts of fatty acids, fatty acid amides, glycerol esters,and fatty imidazolines as disclosed in U.S. Pat. No. 6,372,696, thecontents of which are incorporated by reference herein; frictionmodifiers obtained from a reaction product of a C₄ to C₇₅, preferably aC₆ to C₂₄, and most preferably a C₆ to C₂₀ fatty acid ester and anitrogen-containing compound selected from the group consisting ofammonia, and an alkanolamine, and the like and mixtures thereof.

Examples of antifoaming agents include, but are not limited to, polymersof alkyl methacrylate; polymers of dimethylsilicone, and the like andmixtures thereof.

Each of the foregoing additives, when used, is, used at a functionallyeffective amount to, impart the desired properties to the lubricant.Thus, for example, if an additive is a friction modifier, a functionallyeffective amount of this friction modifier would be an amount sufficientto impart the desired friction modifying characteristics to thelubricant. Generally, the concentration of each of these additives, whenused, ranges from about 0.001% to about 20% by weight, and in oneembodiment about 0.01% to about 10% by weight based on the total weightof the lubricating oil composition.

The final application of the lubricating oil compositions of thisinvention may be, for example, in marine cylinder lubricants incrosshead diesel engines, crankcase lubricants in automobiles andrailroads and the like, lubricants for heavy machinery such as steelmills and the like, or as greases for bearings and the like. In oneembodiment, the lubricating oil compositions of this invention are usedto lubricate a diesel engine such as a heavy duty diesel engine or acompression ignited diesel engine equipped with at least one of anexhaust gas recirculation (EGR) system; a catalytic converter; and aparticulate trap.

Whether the lubricating oil composition is fluid or solid willordinarily depend on whether a thickening agent is present. Typicalthickening agents include polyurea acetates, lithium stearate, and thelike.

The following non-limiting examples are illustrative of the presentinvention.

EXAMPLE 1

A lubricating oil composition was prepared by blending together thefollowing components to obtain a SAE 15W-40 viscosity grade formulation:

(1) 2300 ppm, in terms of sulfur content, of a combination of amethylene bis di-n-butyl dithiocarbamate (0.7 wt. % in the finished oil)and one or more detergents, wherein 1900 ppm of sulfur is derived fromactive sulfur (i.e., methylene bis di-n-butyl dithiocarbamate) and 400ppm of sulfur is derived from nonactive sulfur compound (i.e., thedetergent).

(2) 400 ppm, in terms of boron content, of a combination of a borateddispersant (5.2 wt % in the finished oil) and borated sulfonate (3mmol/kg in the finished oil) having a total, base number (TBN) of 160.

(3) 1200 ppm, in terms of molybdenum content, of a molybdenumsuccinimide complex.

(4) 2.6 wt. % of a dispersant.

(5) 1 wt. % of a diphenylamine antioxidant.

(6) 1 wt. % of a hindered phenol antioxidant.

(7) 0.3 wt. % of a pour point depressant.

(8) 6.6 wt. % of a dispersant viscosity index improver.

(9) 10 ppm, in terms of silicon content, of a foam inhibitor.

The remainder was diluent oil composed of approximately 72 wt. % of aCHEVRON 220N Group II base oil and approximately 28 wt. % of a CHEVRON600N Group II base oil.

The resulting lubricating oil composition had a sulfated ash content of0.3 wt. % as determined by ASTM D874.

COMPARATIVE EXAMPLE A

A lubricating oil composition was prepared by blending together thefollowing components to obtain a SAE 15W-40 viscosity grade formulation:

(1) 400 ppm, in terms of sulfur content, of a nonactive sulfur compound(i.e., a detergent).

(2) 400 ppm, in terms of boron content, of a combination of a borateddispersant (5.2 wt % in the finished oil) and borated sulfonate (3mmol/kg in the finished oil) having a total base number (TBN) of 160.

(3) 90 ppm, in terms of molybdenum content, of a molybdenum succinimidecomplex.

(4) 2.6 wt. % of a dispersant.

(5) 1 wt. % of a diphenylamine antioxidant.

(6) 1 wt. % of a hindered phenol antioxidant.

(7) 0.3 wt. % of a pour point depressant.

(8) 6.6 wt. % of a dispersant viscosity index improver.

(9) 10 ppm, in terms of silicon content, of a foam inhibitor.

(10) The remainder was diluent oil composed of approximately 82 wt. % ofa CHEVRON 220N Group II base oil and approximately 18 wt. % of a CHEVRON600N Group II base oil.

The resulting lubricating oil composition had a sulfated ash content of0.2 wt. % as determined by ASTM D874.

COMPARATIVE EXAMPLE B

A lubricating oil composition was prepared by blending together thefollowing components to obtain a SAE 15W-40 viscosity grade formulation:

(1) 400 ppm, in terms of sulfur content, of a nonactive sulfur compound(i.e., a detergent).

(2) 750 ppm, in terms of boron content, of a combination of a borateddispersant (5.2 wt % in the finished oil), borated calcium sulfonate (3mmol/kg Ca basis in the finished oil) having a TBN of 160, and adispersed hydrated sodium borate (0.5 wt. % in the finished oil).

(3) 90 ppm, in terms of molybdenum content, of a molybdenum succinimidecomplex.

(4) 2.6 wt. % of a dispersant.

(5) 1 wt. % of a diphenylamine antioxidant.

(6) 1 wt. % of a hindered phenol antioxidant.

(7) 0.5 wt. % of a pour point depressant.

(8) 4.1 wt. % of a dispersant viscosity index improver.

(9) 10 ppm, in terms of silicon content, of a foam inhibitor.

(10) The remainder was diluent oil composed of approximately 55 wt. % ofa Group III base oil and approximately 45 wt. % of a Group II base oil.

The resulting lubricating oil composition had a sulfated ash content of0:4 wt. % as determined by ASTM D874.

COMPARATIVE EXAMPLE C

A lubricating oil composition was prepared by blending together thefollowing components to obtain a SAE 15W-40 viscosity grade formulation:

(1) 2300 ppm, in terms of sulfur content, of a combination of amethylene bis di-n-butyl dithiocarbamate (0.7 wt. % in the finished oil)and one or more detergents, wherein 1900 ppm of sulfur is derived fromactive sulfur (i.e., methylene bis di-n-butyl dithiocarbamate) and 400ppm of sulfur is derived from nonactive sulfur compound (i.e., thedetergent).

(2) 750 ppm, in terms of boron content, of a combination of a borateddispersant (5.2 wt. % in the finished oil), borated calcium sulfonate (3mmol/kg Ca basis in the finished oil) having a TBN of 160, and adispersed hydrated sodium borate (0.5 wt. % in the finished oil).

(3) 90 ppm, in terms of molybdenum content, of a molybdenum succinimidecomplex.

(4) 2.6 wt. % of a dispersant.

(5) 1 wt. % of a diphenylamine antioxidant.

(6) 1 wt. % of a hindered phenol antioxidant.

(7) 0.5 wt. % of a pour point depressant.

(8) 6.7 wt. % of a dispersant viscosity index improver.

(9) 10 ppm, in terms of silicon content, of a foam inhibitor.

(10) The remainder was diluent oil composed of approximately 72 wt. % ofa CHEVRON 220N Group II base oil and approximately 28 wt. % of a CHEVRON600N Group II base oil.

The resulting lubricating oil composition had a sulfated ash content of0.4 wt. % as determined by ASTM D874.

Testing

API CJ-4 Cummins ISM Test

The lubricating oil compositions of Example 1 and Comparative ExamplesA-C were evaluated for their wear performance. A screener version of theCJ-4 Cummins engine test was used to determine heavy duty diesel valvetrain wear performance by measuring the injector adjusting screw weightloss (IASWL). The CJ-4 Cummins Test is a Cummins ISM engine equippedwith EGR. The engine test duration is 100 hours. The results for thistest are set forth below in Table 1.

TABLE 1 IASWL Example 1 5.9 Comp. Ex. A 22.3 Comp. Ex. B 31.2 Comp. Ex.C 38.6As the data show, the lubricating oil composition of Example 1significantly reduced the injector screw wear as compared to thelubricating oil compositions of Comparative Examples A-C. Thus, it isbelieved that the lubricating oil composition of the present inventionis capable of providing a surface film on the injector screw that willbe sufficient to provide improved wear benefits.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore the above description should notbe construed as limiting, but merely as exemplifications of preferredembodiments. For example, the functions described above and implementedas the best mode for operating the present invention are forillustration purposes only. Other arrangements and methods may beimplemented by those skilled in the art without departing from the scopeand spirit of this invention. Moreover, those skilled in the art willenvision other modifications within the scope and spirit of the claimsappended hereto.

1. A lubricating oil composition having a sulfur content of up to about0.4 wt. % and a sulfated ash content of up to about 0.5 wt. % asdetermined by ASTM D874 and comprising (a) a major amount of an oil oflubricating viscosity; (b) at least one oil-soluble or dispersedoil-stable boron-containing compound having from about 40 ppm to no morethan about 400 ppm of boron, based upon the total mass of thecomposition; and (c) at least one oil-soluble or dispersed oil-stablemolybdenum-containing compound having at least about 1100 ppm ofmolybdenum, based upon the total mass of the composition; wherein thelubricating oil composition has a ratio of sulfur to molybdenum of about0.5:1 to less than or equal to about 4:1.
 2. The lubricating oilcomposition of claim 1, wherein the oil of lubricating viscosity iscomprised of a mineral base oil. 3.-4. (canceled)
 5. The lubricating oilcomposition of claim 1, having a ratio of sulfur to molybdenum of lessthan about 3:1. 6.-8. (canceled)
 9. The lubricating oil composition ofclaim 1, having a ratio of sulfur to molybdenum of about 1:1 to about2.5:1.
 10. The lubricating oil composition of claim 1, wherein theoil-soluble or dispersed oil-stable molybdenum compound is selected fromthe group consisting of a sulfurized or non-sulfurized molybdenumpolyisobutenyl succinimide complex, molybdenum dithiocarbamate,dispersed hydrated molybdenum compound, acidic molybdenum compound or asalt thereof and mixtures thereof.
 11. (canceled)
 12. The lubricatingoil composition of claim 1, wherein the oil-soluble or dispersedoil-stable molybdenum compound is a molybdenum dithiocarbamate.
 13. Thelubricating oil composition of claim 1, wherein the oil-soluble ordispersed oil-stable molybdenum compound is a sulfurized ornon-sulfurized molybdenum polyisobutenyl succinimide complex.
 14. Thelubricating oil composition of claim 1, wherein the sulfur is derivedfrom a compound selected from the group consisting of a polyisobutyldithiothione, ashless dithiocarbamate and mixtures thereof.
 15. Thelubricating oil composition of claim 1 wherein the sulfur is derivedfrom a bisdithiocarbamate compound of the Formula:

wherein R¹³, R¹⁴, R¹⁵, and R¹⁶ are the same or different and arealiphatic hydrocarbyl groups having 1 to 13 carbon atoms and R¹⁷ is analkylene group having 1 to 8 carbon atoms.
 16. (canceled)
 17. Thelubricating oil composition of claim 1, having a sulfated ash content ofup to about 0.4 wt. % as determined by ASTM D874.
 18. The lubricatingoil composition of claim 1, which is substantially free of phosphorus.19. The lubricating oil composition of claim 1, which is substantiallyfree of zinc dialkyl dithiophosphate.
 20. The lubricating oilcomposition of claim 1, further comprising at least one additiveselected from the group consisting of metallic detergents, ashlessdispersants, friction modifiers, extreme pressure agents, viscosityindex improvers and pour point depressants.
 21. A method of operating aninternal combustion engine comprising the step of operating the internalcombustion engine with a lubricating oil composition having a sulfurcontent of up to about 0.4 wt. % and a sulfated ash content of up toabout 0.5 wt. % as determined by ASTM D874 and comprising (a) a majoramount of an oil of lubricating viscosity; (b) at least one oil-solubleor dispersed oil-stable boron-containing compound having from about 40ppm to no more than about 400 ppm of boron, based upon the total mass ofthe composition; and (c) at least one oil-soluble or dispersedoil-stable molybdenum-containing compound having at least about 1100 ppmof molybdenum, based upon the total mass of the composition; wherein thelubricating oil composition has a ratio of sulfur to molybdenum of about0.5:1 to less than or equal to about 4:1. 22-27. (canceled)
 28. Themethod of claim 21, wherein the lubricating oil composition has a ratioof sulfur to molybdenum of about 1:1 to about 2.5:1.
 29. The method ofclaim 21, wherein the oil-soluble or dispersed oil-stable molybdenumcompound of the lubricating oil composition is selected from the groupconsisting of a sulfurized or non-sulfurized molybdenum polyisobutenylsuccinimide complex, molybdenum dithiocarbamate, dispersed hydratedmolybdenum compound, acidic molybdenum compound or a salt thereof andmixtures thereof.
 30. The method of claim 21, wherein the sulfur of thelubricating oil composition is derived from a compound selected from thegroup consisting of an alkyl or alkenyl sulfide, polyisobutyldithiothione, ashless dithiocarbamate and mixtures thereof. 31.(canceled)
 32. The method of claim 21, wherein the sulfur of thelubricating oil composition is derived from a bisdithiocarbamatecompound of the Formula:

wherein R¹³, R¹⁴, R¹⁵, and R¹⁶ are the same or different and arealiphatic hydrocarbyl groups having 1 to 13 carbon atoms and R¹⁷ is analkylene group having 1 to 8 carbon atoms.
 33. (canceled)
 34. The methodof claim 21, wherein the lubricating oil composition has a sulfated ashcontent of up to about 0.4 wt. % as determined by ASTM D874.
 35. Themethod of claim 21, wherein the lubricating oil composition issubstantially free of phosphorus.
 36. The method of claim 21, whereinthe lubricating oil composition is substantially free of zinc dialkyldithiophosphate.
 37. An internal combustion engine lubricated with thelubricating oil composition of claim
 1. 38.-39. (canceled)